Integrated modeling and systems engineering for the Thirty Meter Telescope

Angeli, George Z.; Vogiatzis, Konstantinos; MacMynowski, Douglas G.; Seo, Byoung-Joon; Nissly, Carl; Troy, Mitchell; Cho, Myung‐Haing

doi:10.1117/12.919363

Cited by 6 publications

(5 citation statements)

References 21 publications

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“…First, the current position of the primary and secondary mirror nodes is calculated by Equation (3). Then, based on the current position of the secondary mirror, the coma-free rotation point of the primary and secondary mirrors is calculated using the coma-free rotation point theory.…”

Section: Process Of Optical Pupil Shift Compensationmentioning

confidence: 99%

“…The gravitational bending and sinking of the secondary mirror, as well as changes in the relative position of the primary and secondary mirrors due to temperature changes, are the main causes of the misalignment error of an optical system. After the optical system is folded into the Couder imaging system, it causes the system optical axis, and consequently the system optical pupil position, to shift [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

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Optical Pupil Shift Correction Method for Large Ground-Based Optical Telescopes

Wang,

Cao

et al. 2023

Applied Sciences

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Cassegrain telescopes with larger apertures suffer significant optical pupil shifting errors caused by gravity and temperature gradients. This study constructs an optical model of a large Cassegrain telescope and a method to calculate and compensate its shifting error. First, the optical structure is simplified by incorporating only the most relevant telescope components, and the system optics is modeled using ray tracing. A computer-aided mounting-based method for calculating the misalignment error of primary and secondary mirrors is proposed, with the spatial position change of secondary mirrors as the input. Next, a compensation method based on the coma-free point theory of the Cassegrain system is proposed, with the main mirror’s optical axis as the reference. Finally, using a 4 m aperture telescope as an example, the gravity- and thermal-deformation-induced shifting error is simulated. Based on this simulation, the secondary mirror position is adjusted using a secondary mirror-adjustment mechanism Hexapod platform to compensate for the misalignment error. Both gravity and temperature are major causes of shift in the pupil position, with a maximum shift of 18 mm. After compensation, this shift is controlled within 1 mm. The modeling method and the simulation process mentioned in this research can also be used in the other relevant fields.

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Section: Process Of Optical Pupil Shift Compensationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optical Pupil Shift Correction Method for Large Ground-Based Optical Telescopes

Wang,

Cao

et al. 2023

Applied Sciences

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show abstract

“…The ongoing development of subsystem-level requirements, designs, analyses, and prototype test results is progressing, as is described in other papers presented at this symposium [2][3][4][5][6][7][8][9][10] .…”

Section: Introductionmentioning

confidence: 96%

First light adaptive optics systems and components for the Thirty Meter Telescope

et al. 2010

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Adaptive optics (AO) is essential for many elements of the science case for the Thirty Meter Telescope (TMT). The initial requirements for the observatory's facility AO system include diffraction-limited performance in the near IR, with 50 per cent sky coverage at the galactic pole. Point spread function uniformity and stability over a 30 arc sec field-ofview are also required for precision photometry and astrometry. These capabilities will be achieved via an order 60x60 multi-conjugate AO system (NFIRAOS) with two deformable mirrors, six laser guide star wavefront sensors, and three low-order, IR, natural guide star wavefront sensors within each client instrument. The associated laser guide star facility (LGSF) will employ 150W of laser power at a wavelength of 589 nm to generate the six laser guide stars.We provide an update on the progress in designing, modeling, and validating these systems and their components over the last two years. This includes work on the layouts and detailed designs of NFIRAOS and the LGSF; fabrication and test of a full-scale prototype tip/tilt stage (TTS); Conceptual Designs Studies for the real time controller (RTC) hardware and algorithms; fabrication and test of the detectors for the laser-and natural-guide star wavefront sensors; AO system modeling and performance optimization; lab tests of wavefront sensing algorithms for use with elongated laser guide stars; and high resolution LIDAR measurements of the mesospheric sodium layer. Further details may be found in specific papers on each of these topics.

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“…and observing orientation. 6 The resulting probability distribution for the mean Ml wind peed u is shown in Fig. 2 Static forces are completely corrected by t he integral control of MICS: it is only the unsteady (turbulent) forces that lead to residual segment dynamic response.…”

Section: Wind Loads and Response 21 Wind Disturbance Characterismentioning

confidence: 99%

Primary mirror dynamic disturbance models for TMT: vibration and wind

et al. 2010

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The principal dynamic disturbances acting on a telescope segmented primary mirror are wlSteady wind pressure (turbulence) and narrowband vibration from rotating equipment. Understanding these disturbances is essential for the design of the segment support assembly (SSA) , segment actuators, and primary mirror control system (M I CS) . The wind dist urbance is relatively low frequency, and is partially compensated by MICS; the response depends on the control bandwidth and the quasi-static tiffness of the actuator and SSA. Equipment vibration is at frequencies higher than the MICS bandwidth; the response depends on segment damping, and the proximity of segnlent support resonances to dominant vibration tones. We present here both disturbance models and parametric response. Wind modeling is informed by CFD and based on propagation of a von Karman pressure screen. The vi bration model is informed by analysis of accelerometer and adaptive optics data from Keck. TillS information is extrapolated to T 1T and applied to the telescope structural model to understand the response dependence on actuator design parameters in particular. Whether the vibration response or the wind response is larger depends on these design choices; "soft" (e.g. voice-coil) actuators provide better vibration reduction but require high servo bandwidth for wind rejection, willie "hard" (e.g. piezo-electric) actuators provide good wind rejection but require damping to avoid excessive vibration transmission to the primary mirror segments. The results for both nominal and worst-case disturbances and design parameters are incorporated into the TMT actuator performance assessment.

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Integrated modeling and systems engineering for the Thirty Meter Telescope

Cited by 6 publications

References 21 publications

Optical Pupil Shift Correction Method for Large Ground-Based Optical Telescopes

Optical Pupil Shift Correction Method for Large Ground-Based Optical Telescopes

First light adaptive optics systems and components for the Thirty Meter Telescope

Primary mirror dynamic disturbance models for TMT: vibration and wind

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